1. Field of the Invention
The present invention relates to a structure for mounting a level gage with respect to a liquid storage container which is provided on a vehicle, an industrial machine, an instrument or the like.
2. Description of the Related Art
There are known various types of level gage for detecting the levels of petroleum, water and various kinds of medicine which are stored in containers such as tanks. Among them is one type of level gage which is described in, for example, the specification of U.S. Pat. No. 4,627,280.
This level gage 50 comprises, as shown in FIG. 14, a casing 54, a core 56 inserted inside the casing 54, a coil 57 wound around the core 56, and an electrically conductive ring 58 vertically movably fitted on the outer periphery of the casing 54.
The casing 54 is secured at its upper portion to an upper member 52 of a storage container 51. The electrically conductive ring 58 is secured to a float 59 so that the ring 58 floats on a liquid 53 and moves vertically along the periphery of the casing 54. In this level gage 50, the electrically conductive ring 58 moves vertically in accordance with the change in the liquid level 64 as a result of increase or decrease of the liquid 53 in the storage container 51. The inductance of the coil 57 changes in response to the vertical movement of the ring 58, and the change in conductance enables the liquid level to be accurately detected through a meter or other similar means.
However, when the internal pressure of the storage container 51 is raised above normal pressures by, for example, a rise in temperature, the lower member 55 of the container 51 may be inflated downward as shown by the two-dot chain line in the figure. In such a case, even if the amount of liquid 53 stored in the container 51 is constant, the liquid level 64 lowers as shown by the two-dot chain line. Further, the upper member 52 of the container 51 is also inflated as shown by the two-dot chain line, so that the installation position of the level gage 50 which is rigidly secured to the upper member 52 becomes higher than that in the case of normal pressures. Accordingly, there may be an error in the level 64 detected by the level gage 50, disadvantageously.
Problems arise due to the container's deflation when the internal pressures of the storage container 51 lowers below normal pressures.
In view of the above-described circumstances, the present inventors made exhaustive study to obtain a structure for mounting the level gage 50 which enables minimization of the above-described error, and found the fact that said object is attained by providing the level gage 50 inside the storage container 51 in such a manner that the lower end of the level gage 50 is supported on the bottom surface of the storage container 51 so that the level gage 50 is allowed to vertically move in response to the vertical movement of the bottom surface of the lower member 55 relative to the upper member 52. However, there are still problems as follows.
The first problem is to design a structure for constantly biasing the level gage 50 toward the bottom surface of the storage container 51, and the second problem is to find an effective way in which the level gage 50, particularly the upper end thereof, is supported inside the storage container 51.
The coil 57 consists of two portions, that is, a densely wound coil portion 61 which is formed by densely winding a conductor around the outer periphery of the upper part of the core 56 and a coarsely wound coil portion 62 which is formed by coarsely winding a conductor below the densely wound coil portion 61.
However, the diameter of the portion (the head portion 63) of the casing 54 which has the densely wound coil portion 61 is larger than that of the portion (the guide portion) of the casing 54 which incorporates the coarsely wound coil portion 62. Accordingly, when a liquid is supplied into the storage container 51 and the electrically conductive ring 58 is thereby raised, the ring 58 comes into contact with the head portion 63 as shown by the two-dot chain line in FIG. 14, which makes it impossible to detect the liquid level 64.
Accordingly, it is impossible with the above-described technique to detect the liquid level 64 when the storage container 51 is filled up with the liquid 53. Therefore, it is general practice to use the container 51 in such a manner that it is not filled up with the liquid 53, which disadvantageously lowers the service efficiency of the storage container 51.